The Elasticity of Polymer Melts and Solutions in Shear and Extension Flows

This review is devoted to understanding the role of elasticity in the main flow modes of polymeric viscoelastic liquids-shearing and extension. The flow through short capillaries is the central topic for discussing the input of elasticity to the effects, which are especially interesting for shear. An analysis of the experimental data made it possible to show that the energy losses in such flows are determined by the Deborah and Weissenberg numbers. These criteria are responsible for abnormally high entrance effects, as well as for mechanical losses in short capillaries. In addition, the Weissenberg number determines the threshold of the flow instability due to the liquid-to-solid transition. In extension, this criterion shows whether deformation takes place as flow or as elastic strain. However, the stability of a free jet in extension depends not only on the viscoelastic properties of a polymeric substance but also on the driving forces: gravity, surface tension, etc. An analysis of the influence of different force combinations on the shape of the stretched jet is presented. The concept of the role of elasticity in the deformation of polymeric liquids is crucial for any kind of polymer processing.

Automated summary

This review focuses on the role of elasticity in the shearing and extension flow modes of polymeric viscoelastic liquids. Experimental data analysis reveals that energy losses in these flows are determined by the Deborah and Weissenberg numbers. These criteria not only govern the abnormally high entrance effects and mechanical losses in short capillaries, but also determine the threshold for flow instability caused by the liquid-to-solid transition. Additionally, the Weissenberg number determines whether deformation occurs as flow or elastic strain in extension. The stability of a free jet in extension depends on both the viscoelastic properties of the polymeric substance and external driving forces, such as gravity and surface tension. An analysis of different force combinations on the shape of the stretched jet is presented. The concept of the role of elasticity in the deformation of polymeric liquids is crucial for polymer processing.